This invention relates to an overedge width regulating device for overedging sewing machines.
Conventionally, it is often necessary when using overedging sewing machines to take into account the material and the number of overlayed fabrics of the workpiece to determine the overedge width to meet the requirements of the particular application. To adjust the overedge width, the operator ordinarily has to change the throat plate for one which has a suitable overedge-width latch.
Where a sewing machine is equipped with a throat plate which has an adjustable overedge-width latch, an operator has to manually adjust the overedge width by moving the overedge-width latch back and forth, or left and right, and then has to adjust the position of the lower knife to meet with the adjusted overedge width. To do so, an operator typically has to open a cover sheet located under the table supporting the sewing machine to expose the lower knife. Such operations are very troublesome.
Further, adjustments of the lower knife are generally accomplished by loosening and tightening screws which fix the knife to the machine. Consequently, such manipulations not only require the operator's expertise, but, as well, considerable loss of time is expected.
For the purpose of overcoming the above-mentioned disadvantages, Japanese Laid Open Utility Model Application No. 59-67169 discloses a device for regulating the overedge width by adjusting both the overadge-width latch and the lower knife simultaneously.
Referring more specifically to FIG. 5 herein, key-points of the Japanese Laid Open Application will now be explained. In FIG. 5, numeral 21 denotes a throat plate and numeral 22 denotes a throat-plate pin which is extended from the throat plate 21 in the direction of feeding (arrow "A"). Numeral 23 denotes an overedge-width latch which is set in parallel with the throat-plate pin 22 and its rear end is fixed to a movable piece 26 via a fixing block 24. The movable piece 26 is slidably attached to move up and down to a lower knife holder 27 which holds a lower knife 16 via a guide channel 28 and a presser plate 29. A control shaft 31 is provided with male screw threads 35 which cooperate with female screw threads 36 provided in the lower knife holder 27. Control shaft 31 is further provided with a knob 37 at its end.
By rotating only the knob 37, the lower knife holder 27 and the movable piece 26 are moved simultaneously in a direction normal to the feeding direction. Thus, the lower knife 16 and the overedge-width latch 23 move in the same direction and the overedge width is adjusted simply by rotating the knob 37 alone.
Accordingly, for a conventional type of overedging sewing machine such as that briefly described above, the purpose of one-touch adjusting of both the overedge-width latch 23 and the position of the lower knife 16 is achieved by the apparatus of FIG. 5. However, since the overedge-width latch 23 is attached to the lower knife holder 27, it is difficult to minutely adjust the relative position between the overedge-width latch 23 and the lower knife 16.
In some cases, where the workpiece material is knitted fabric, the fabric shrinks during the overedging process and the threads are not tightly overedged. Consequently, in such cases conventional overedging sewing machines do not satisfy the requirements for making such adjustments.
It is, therefore an object of the invention to provide a device which eliminates the aforementioned disadvantages of conventional overedging sewing machines and which enables simultaneous adjustment of both the overedge-width latch and the lower knife, while, at the same time, enables adjustments of the position of the overedge-width latch in relation to the position of the lower knife.